Dictionary.com
definitions
  • synonyms

os1

[os]
See more synonyms on Thesaurus.com
noun, plural os·sa [os-uh] /ˈɒs ə/.
  1. Anatomy, Zoology. a bone.
Show More

Origin of os1

Borrowed into English from Latin around 1540–50

os2

[os]
noun, plural o·ra [awr-uh, ohr-uh] /ˈɔr ə, ˈoʊr ə/.
  1. Anatomy, Zoology. a mouth or orifice of the body.
Show More

Origin of os2

First recorded in 1730–40, os is from the Latin word ōs mouth

os3

[ohs]
noun, plural o·sar [oh-sahr] /ˈoʊ sɑr/.
  1. Geology. an esker, especially when of great length.
Show More

Origin of os3

< Swedish ås (plural åsar) ridge

Os

  1. Symbol, Chemistry. osmium.
Show More

OS

  1. Old Saxon.
  2. Computers. operating system.
Show More

O, o

[oh]
noun, plural O's or Os; o's or os or oes.
  1. the fifteenth letter of the English alphabet, a vowel.
  2. any spoken sound represented by the letter O or o, as in box, note, short, or love.
  3. something having the shape of an O.
  4. a written or printed representation of the letter O or o.
  5. a device, as a printer's type, for reproducing the letter O or o.
Show More

O

[oh]
interjection
  1. (used before a name in direct address, especially in solemn or poetic language, to lend earnestness to an appeal): Hear, O Israel!
  2. (used as an expression of surprise, pain, annoyance, longing, gladness, etc.)
Show More
noun, plural O's.
  1. the exclamation “O.”
Show More

Origin of O

1125–75; Middle English < Old French < Latin ō
Can be confusedO oh owe

o/s

  1. (of the calendar) Old Style.
  2. out of stock.
  3. (in banking) outstanding.
Show More

O/S

  1. (of the calendar) Old Style.
Show More

O.S.1

or o.s.

  1. (in prescriptions) the left eye.
Show More

Origin of O.S.1

From the Latin word oculus sinister

O.S.2

  1. Old Saxon.
  2. Old School.
  3. Old series.
  4. (of the calendar) Old Style.
  5. Also o.s. ordinary seaman.
Show More
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for os

Contemporary Examples

Historical Examples


British Dictionary definitions for os

os1

noun plural ossa (ˈɒsə)
  1. anatomy the technical name for bone
Show More

Word Origin

C16: from Latin: bone; compare Greek osteon

os2

noun plural ora (ˈɔːrə)
  1. anatomy zoology a mouth or mouthlike part or opening
Show More

Word Origin

C18: from Latin

os3

noun plural osar (ˈəʊsɑː)
  1. another name for esker
Show More

Word Origin

C19 osar (pl), from Swedish ås (sing) ridge

Os

the chemical symbol for
  1. osmium
Show More

OS

abbreviation for
  1. Old School
  2. Old Style (method of reckoning dates)
  3. Ordinary Seaman
  4. (in Britain) Ordnance Survey
  5. outsize
  6. Old Saxon (language)
Show More

o

O

noun plural o's, O's or Os
  1. the 15th letter and fourth vowel of the modern English alphabet
  2. any of several speech sounds represented by this letter, in English as in code, pot, cow, move, or form
  3. another name for nought
Show More

o.s.

OS or O/S

abbreviation for
  1. out of stock
  2. banking outstanding
Show More

O1

symbol for
  1. chem oxygen
  2. a human blood type of the ABO groupSee universal donor
  3. logic a particular negative categorial proposition, such as some men are not married: often symbolized as SoPCompare A, E, I 2
Show More
abbreviation for
  1. Australian slang offence
Show More

Word Origin

(for sense 3) from Latin (neg) o I deny

O2

interjection
  1. a variant spelling of oh
  2. an exclamation introducing an invocation, entreaty, wish, etcO God!; O for the wings of a dove!
Show More
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for os

o

interjection of fear, surprise, admiration, etc.; see oh.

Show More

O

blood type, 1926, originally "zero," denoting absence of A and B agglutinogens.

Show More
Online Etymology Dictionary, © 2010 Douglas Harper

os in Medicine

Os

  1. The symbol for the elementosmium

OS


os in Science

Os

O

osmium

[ŏzmē-əm]
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.